Weightbearing simulation assembly and methods of using the same to image a subject

ABSTRACT

A weightbearing simulation assembly includes a substrate comprising a mounting surface extending in a first direction a subject support disposed on a first region of the mounting surface and a pedal assembly disposed on a second region of the mounting surface. The pedal assembly includes a spring assembly including a contact plate facing the subject support, a compression plate, and a first spring disposed between the contact plate and the compression plate. A subject applies a compressive force to the contact plate in a compression direction to simulate a load-bearing condition by compressing the first spring. An orientation of the pedal assembly may be adjusted to change a relative angle between the compression direction and the first direction to alter an imaging angle.

BACKGROUND Field

The present application generally relates to medical imaging and, moreparticularly, to devices and methods for simulating weightbearingconditions to generate medical images of subjects' lower extremities viavarious modalities, such computed tomography or magnetic resonancetomography.

Technical Background

In order to accurately assess a subject's lower extremities (e.g., hip,knee, foot, ankle, or the like) to plan treatment for conditionstherein, it is beneficial to obtain structural measurements of thesubject's lower extremities. For certain conditions (e.g., Halluxvalgus), it is beneficial to obtain three-dimensional structuralmeasurements of the subject in a loadbearing condition. Existingthree-dimensional medical imaging systems (e.g., computed tomographyscanners and magnetic resonance imaging systems) present variousconstraints for creating such a loadbearing condition during imaging toobtain three-dimensional structural measurements. For example, existingbore scanners commonly extend in a horizontal direction, renderinggravity unavailable to supply a normal load to the subject's foot duringimaging. Further, existing vertical bore scanners that allow a subjectto stand while scanning is completed are extremely expensive, difficultto use, and do not enjoy widespread adoption.

SUMMARY

According to an embodiment of the present disclosure a weightbearingsimulation assembly includes a substrate including a mounting surfaceextending in a first direction; a subject support disposed on a firstregion of the mounting surface; and a pedal assembly disposed on asecond region of the mounting surface. The pedal assembly is spacedapart from the subject support by a distance in the first direction. Thepedal assembly includes a spring assembly comprising a contact platefacing the subject support, a compression plate, and a first springdisposed between the contact plate and the compression plate, the springextending in a compression direction. The pedal assembly also includes afirst motion limiter extending through the compression plate, an end ofthe first motion limiter is disposed between the compression plate andthe contact plate to limit a range of motion of the contact plate in thecompression direction. The contact plate contacts the first motionlimiter at an end of the range of motion to place the first spring intoa loaded state when a subject applies a compressive force to the contactplate. The pedal assembly also includes a pedal support assemblydisposed on the mounting surface, the pedal support assembly defining acavity in which the spring assembly is disposed. The pedal assembly alsoincludes an adjustable support element for the pedal support assembly,the adjustable support element includes a plurality of support positionsselectable to adjust an orientation of the pedal support assembly tochange a relative angle between the compression direction and the firstdirection.

In another embodiment, a subject imaging assembly includes a supportplatform extending in a first direction, the support platform includingan engagement element. The subject imaging assembly also includes animaging system including a gantry, the gantry including an opening. Thesubject imaging assembly also includes a weightbearing simulationassembly disposed on the support platform, the weightbearing simulationassembly includes a substrate coupled to the engagement element of thesupport platform, the substrate including a mounting surface extendingin the first direction. The weightbearing simulation assembly alsoincludes a subject support disposed on a first region of the mountingsurface, the subject support rotatable about an axis of rotation tofacilitate positioning the subject support relative to the gantry. Theweightbearing simulation assembly also includes a pedal assemblydisposed on a second region of the mounting surface, n the pedalassembly is spaced apart from the subject support by a distance in thefirst direction. The pedal assembly includes a spring assemblycomprising a contact plate facing the subject support, a compressionplate, and a spring disposed between the contact plate and thecompression plate, the spring extending in a compression direction and amotion limiter extending from the compression plate. An end of themotion limiter is disposed between the compression plate and the carrierplate to limit a range of motion of the contact plate in the compressiondirection. The pedal assembly also includes a pedal support assemblydisposed on the mounting surface, the pedal support assembly supportingthe spring assembly on the mounting surface. The subject imagingassembly further includes an actuator coupled to the substrate of theweightbearing simulation assembly, the actuator configured to move theweightbearing simulation assembly in the first direction such that thepedal assembly is disposed within the opening to generate an image.

In another embodiment, a method of capturing an image of a lowerextremity of a subject includes positioning a subject on a subjectsupport of a weight simulation assembly disposed on a support platformof an imaging system. The weight simulation assembly comprises asubstrate extending in the first direction, a subject support disposedon a first region of the substrate, and a pedal assembly disposed on asecond region of the substrate. The pedal assembly is spaced apart fromthe subject support by a distance in the first direction. The methodalso includes adjusting a motion limiter disposed between a contactplate facing the subject support and a compression plate of the pedalassembly so as to change a range of motion of the contact plate withinthe pedal assembly in a compression direction and create a load tailoredto the subject when the contact plate is in a fully pressed position.The method also includes adjusting a relative angle between thecompression direction and the first direction so as to adjust an angleof the lower extremity in the pedal assembly. The method also includespositioning the weightbearing simulation assembly relative to a gantryof an imaging system such that the pedal assembly is disposed within anopening of the gantry. The method also includes, once the subjectapplies the load tailored to the subject to the contact plate via thelower extremity so as to bring the contact plate in contact with themotion limiter, capturing an image of the lower extremity using theimaging system.

Additional features and advantages of the processes and systemsdescribed herein will be set forth in the detailed description whichfollows, and in part will be readily apparent to those skilled in theart from that description or recognized by practicing the embodimentsdescribed herein, comprising the detailed description which follows, theclaims, as well as the appended drawings.

It is to be understood that both the foregoing general description andthe following detailed description describe various embodiments and areintended to provide an overview or framework for understanding thenature and character of the claimed subject matter. The accompanyingdrawings are comprised to provide a further understanding of the variousembodiments, and are incorporated into and constitute a part of thisspecification. The drawings illustrate the various embodiments describedherein, and together with the description serve to explain theprinciples and operations of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments set forth in the drawings are illustrative and exemplaryin nature and not intended to limit the subject matter defined by theclaims. The following detailed description of the illustrativeembodiments can be understood when read in conjunction with thefollowing drawings, where like structure is indicated with likereference numerals and in which:

FIG. 1A depicts a perspective view of a subject imaging assembly,according to one or more embodiments described herein;

FIG. 1B depicts another perspective view of the subject imaging assemblyshown in FIG. 1A, according to one or more embodiments described herein;

FIG. 1C depicts another perspective view of the subject imaging assemblyshown in FIG. 1A with a subject positioned thereon, according to one ormore embodiments described herein;

FIG. 2 depicts a perspective view of a support platform of a subjectimaging assembly supporting a substrate of a weightbearing simulationassembly, according to one or more embodiments described herein;

FIG. 3A depicts a perspective view of a substrate of a weightbearingsimulation assembly including a mounting element, according to one ormore embodiments described herein;

FIG. 3B depicts a perspective view of the substrate depicted in FIG. 3Aattached to a support platform of a subject imaging assembly via themounting element, according to one or more embodiments described herein;

FIG. 4A depicts a perspective view of an underside surface of asubstrate of a weightbearing simulation assembly including an attachmentelement, according to one or more embodiments described herein;

FIG. 4B depicts a perspective view of a mounting surface of a supportplatform of an imaging assembly including a support element forreceiving the attachment element depicted in FIG. 4A, according to oneor more embodiments described herein;

FIG. 5A depicts a perspective view of a weightbearing simulationassembly, according to one or more embodiments described herein;

FIG. 5B depicts a perspective view of a weightbearing simulationassembly, according to one or more embodiments described herein;

FIG. 6A depicts a perspective view of a pedal assembly, according to oneor more embodiments described herein;

FIG. 6B depicts another perspective view of the pedal assembly shown inFIG. 6A, according to one or more embodiments described herein;

FIG. 6C depicts an exploded view of the pedal assembly shown in FIG. 6A,according to one or more embodiments described herein;

FIG. 6D depicts a perspective view of the pedal assembly shown in FIG.6A in a loaded state, according to one or more embodiments describedherein;

FIG. 6E depicts a perspective view of the pedal assembly shown in FIG.6A in an unloaded state, according to one or more embodiments describedherein;

FIG. 6F depicts a perspective view of the pedal assembly shown in FIG.6A having a compression direction in an alternative orientation,according to one or more embodiments described herein;

FIG. 7 depicts a perspective view of a motion limiter for a pedalassembly, according to one or more embodiments described herein;

FIG. 8 depicts a perspective view of a gear assembly for a pedalassembly, according to one or more embodiments described herein;

FIG. 9 depicts a perspective view of a pedal assembly, according to oneor more embodiments described herein; and

FIG. 10 depicts a flow diagram of a method for capturing an image of asubject using a weightbearing simulation assembly, according to one ormore embodiments described herein.

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments of a weightbearingsimulation assembly for imaging a lower extremity (e.g., a foot, anankle, a leg, a knee, a hip, or the like) of a subject and methods forusing the same for imaging a subject. The weightbearing simulationassembly may include a substrate on which a subject support and a pedalassembly are disposed. In embodiments, the substrate of theweightbearing simulation assembly is disposed on a support platform of asubject imaging assembly. The subject imaging assembly may include animaging system such as a computer tomography (CT) scanner or a magneticresonance imaging (MRI) system. The relative positioning of theweightbearing simulation assembly and the imaging system may beadjustable (e.g., via an actuator of the support platform) such that thepedal assembly may be movable to a field of view of the imaging system.In embodiments, the pedal assembly includes a spring assembly includinga contact plate facing the subject support and a compression plateseparated by at least one spring member.

In an aspect of the present disclosure, the subject supplies acompressive force to the pedal assembly to place the pedal assembly inan imaging position. In response to the subject supplying thecompressive force to compress the spring member, the contact plate movesin a compression direction until the contact plate contacts motionlimiters of the spring assembly disposed between the contact plate andthe compression plate. Once the contact plate contacts the motionlimiter, the contact plate is disposed an imaging distance from thecompression plate. The spring member supplies resistance to the subjectso as to measure the force provided by the subject. In embodiments, themotion limiters are adjustable so as to change the imaging distance andthe resistance supplied by the at least one spring member in thepresence of the compressive force supplied by the subject. Inembodiments, the resistance supplied by the spring member may beindividually tailored to the subject to simulate a weightbearingcondition for the subject for capturing an image of the subject's lowerextremities. Beneficially, the motion limiters provide a visualindication of whether the subject has supplied an adequate compressiveforce to simulate a weightbearing condition. Additionally, the motionlimiters may be distributed to ensure that the subject properlydistributes the compressive force throughout an entirety of thesubject's foot, preventing the subject from applying too much forceusing one area of the foot (e.g., a heel) and too little force withanother (e.g., a forefoot).

The weightbearing simulation assembly described herein is adaptable tovarious different imaging positions. For example, the pedal assemblydescribed herein includes a pedal support assembly supporting the springassembly and an adjustable support element coupling the pedal supportassembly to the substrate of the weightbearing simulation assembly. Theadjustable support element may include a plurality of support positionsto support the pedal support assembly at various orientations. Inembodiments, selection among the different orientations alters arelative angle between the compression direction of the spring assemblyand an axis of the imaging system to change an angle of the subject'sfoot included in captured images. The plurality of support positions ofthe adjustable support element may facilitate capturing images of asubject's ankle, forefoot, and hindfoot with predetermined loads appliedto each thereof.

Additionally, the subject support may be configurable for a plurality ofdifferent imaging situations. For example, in embodiments, the subjectsupport is rotatably coupled to the substrate such that the subjectsupport is rotatable about a first axis of rotation that issubstantially parallel to a surface normal of the substrate tofacilitate positioning the subject on the weightbearing simulationassembly. In embodiments, the subject support is also rotatable about asecond axis of rotation that is substantially perpendicular to the firstaxis of rotation to facilitate tilting the positioned patent withrespect to the imaging system to facilitate the imaging system beingtilted at various angles for additional imaging flexibility. Moreover,the subject support may also be attached to the substrate via atranslation support mechanism facilitating adjusting a distance betweenthe pedal assembly and the subject support for accommodating subjectshaving different leg lengths. As such, the weightbearing simulationassemblies described herein facilitate capturing a plurality ofdifferent load-bearing images of the subject's lower extremities in amanner particularly tailored to the subject, thus capturing a completethree-dimensional image for diagnosis and treatment of variousconditions.

Beneficially, the weightbearing simulation assemblies described hereinrequire a subject to supply a compressive force to a pedal assembly witha specified foot (e.g., a foot causing the subject discomfort). Byproviding an indication (e.g., the contact plate contacting the motionlimiter) that the subject has supplied a desired amount compressiveforce, the weightbearing simulation assemblies described herein preventthe subject from off-loading from the specified foot in order to ensurethat the specified foot is under a true weightbearing condition. Such aweightbearing condition beneficially facilitates the components ofsubject's foot being accurately imaged in a functional state. Moreover,compatibility with existing horizontal CT scanners enablesthree-dimensional functional imaging of the subject's foot at relativelylow cost for diagnosing subject foot conditions as compared to existingweightbearing CT scanners. Additionally, the approaches described hereinare beneficial over existing weightbearing x-ray imaging techniquesbecause the weightbearing simulation assemblies described hereinfacilitate weightbearing imaging with three-dimensional modalities(e.g., CT scanning, MRI, etc.).

Referring now to FIGS. 1A-1C, a subject imaging assembly 100 isdepicted. The subject imaging assembly 100 is depicted to include asupport platform 102, an imaging system 106, and a weightbearingsimulation assembly 112. In embodiments, the support platform 102 andthe imaging system 106 may be derived from an existing medical imagingsystem such as a computed tomography (CT) scanner or a magneticresonance imaging (MRI) system. For example, in embodiments, the supportplatform 102 may comprise a table top of an existing CT scanner with thebedding removed to provide a surface for attaching the weightbearingsimulation assembly 112. As depicted in FIG. 1C, the support platform102 comprises an engagement element 104 that couples to a complementaryelement of the weightbearing simulation assembly 112. The engagementelement 104 comprises a channel (or a plurality of channels) adapted toreceive a substrate 114 of the weightbearing simulation assembly 112. Itshould be appreciated that the support platform 102, the engagementelement 104, and the complementary element of the substrate 114 may takea variety of forms depending on the implementation. The weightbearingsimulation assembly 112 and the associated substrate 114 may be adaptedto fit to any available subject imaging system. As such, the dimensionsof the substrate 114 and any mechanisms incorporated in theweightbearing simulation assembly 112 for attaching the substrate 114 tothe support platform 102 may vary depending on the subject imagingsystem into which the weightbearing simulation assembly 112 is beingincorporated.

The support platform 102 and substrate 114 of the weightbearingsimulation assembly 112 both extend in a first direction (e.g., thex-direction of the coordinate axes shown in FIGS. 1A-1C). As depicted inFIG. 1B, the support platform 102 is substantially aligned with anopening 110 of a gantry 108 of the imaging system 106. In embodiments,the imaging system 106 comprises an imaging axis (not depicted)extending in the first direction through the opening 110. Inembodiments, the gantry 108 includes a radiation source (e.g., an x-raysource, not depicted) that transmits radiation through the opening 110and a detector (not depicted) for detecting the radiation transmittedthrough a subject (e.g., a subject 132) disposed in the opening 110 (SeeFIG. 1C). The radiation source and detector may be disposed in arotating ring (not depicted) of the gantry 108 that rotates about theimaging axis to generate a three-dimensional image of the subject basedon the radiation transmitted through the subject. In embodiments, theimaging system 106 comprises a CT scanner or an MRI system.

In embodiments, the support platform 102 comprises an actuator 128 (seeFIG. 1C) adapted to translate an element (e.g., the substrate 114 of theweightbearing simulation assembly 112) in the first direction. Theactuator 128 may comprise any mechanism capable of providing relativemotion between the weightbearing simulation assembly 112 and the imagingsystem 106 in the first direction. For example, in embodiments, theactuator 128 is an element (not depicted) that translates within theengagement element 104 to press against the substrate 114 withsufficient force move the substrate 114 in the first direction with asubject 132 disposed thereon. With such movements, the substrate 114 maymove in the first direction such that a portion of the substrate 114 issupported within the opening 110 such that a pedal assembly 122 of theweightbearing simulation assembly 112 is disposed within a field of viewof the imaging system 106 to capture an image of a lower extremity ofthe subject 132. In embodiments, the support platform 102 comprises anentire portion (e.g., tabletop) including the engagement element 104that is movable in the first direction such that a combination of theportion of the support platform 102 and the weightbearing simulationassembly 112 is moved into the opening 110. It should be appreciatedthat certain embodiments may not include a support platform 102. Forexample, in such embodiments, the weightbearing simulation assembly 112may be disposed on a support (e.g., a cart) that is completely separatefrom the imaging system 106.

The weightbearing simulation assembly 112 comprises a substrate 114having a mounting surface 116, a subject support 118 disposed on themounting surface 116 and a pedal assembly 122 disposed on the mountingsurface 116. The subject support 118 is separated from the pedalassembly 122 by a distance 124 in the first direction. In embodiments,the substrate 114 is constructed of a material (e.g., carbon fiber) thatdoes not interfere with the imaging capabilities of the imaging system106. As described herein, the substrate 114 may possess any size, shape,and configuration based on specifications of the incorporating imagingsystem 106.

As depicted in FIG. 1C, in embodiments, the subject support 118 iscoupled to the mounting surface 116 via a translation support mechanism134 such that the distance 124 between the pedal assembly 122 and thesubject support 118 is adjustable to accommodate different subjects 132.The translation support mechanism 134 includes one or more tracks (e.g.,a pair of tracks) that mate with corresponding mounting brackets 136 ofthe subject support 118. In embodiments, fasteners (not depicted)coupling the mounting brackets 136 to the translation support mechanism134 may be loosened and the distance 124 may be manually adjusted to aparticular subject 132. Alternative translation support mechanisms 134are envisioned. In embodiments, the translation support mechanism 134comprises an actuator (e.g., a translation stage) coupling the subjectsupport 118 to the mounting surface 116 such that the distance 124 maybe adjusted electronically. In embodiments, the translation supportmechanism 134 is disposed on a mounting platform (not depicted) attachedto the substrate 114. The mounting platform may be movable (e.g., via atelescoping arm or the like) in a second direction (e.g., thez-direction depicted in FIG. 1C) substantially perpendicular to thefirst direction.

In embodiments, the subject support 118 may be rotatably coupled to thetranslation support mechanism 134. For example, in embodiments, thetranslation support mechanism 134 includes a mounting platform (notdepicted) to which the subject support 118 is attached. The mountingplatform may be rotatable with respect to the remainder of thetranslation support mechanism 134 such that the subject support 118 isrotatable about first axis of rotation 120 that extends substantiallyperpendicular (e.g., in the z-direction of the coordinate axes depictedin FIGS. 1A-1C) to the first direction. Such rotation may facilitatepositioning (e.g., seating) the subject on the subject support 118.After the subject 132 is initially positioned on the subject support118, the subject support 118 may be rotated such that a leg of thesubject 132 (e.g., after the foot of the subject 132 is positioned onthe pedal assembly 122) is aligned in the first direction for imaging.In embodiments, the subject support 118 is rotatable about a second axisof rotation (not depicted) that is substantially perpendicular to thefirst axis of rotation 120 (e.g., in the y-direction of the coordinateaxes depicted in FIGS. 1A-1C) to facilitate tilting the subject relativeto the gantry 108 so that the gantry 108 does not contact the subject132 when rotated about a rotation axis extending in the y-direction.

In embodiments, the subject support 118 is coupled to the translationsupport mechanism 134 via a height adjusting element (not depicted). Inembodiments, the height adjusting element may be similar in structure tothe height adjusting element 536 described herein with respect to FIG.5B. Adjustment of the distance between the subject support 118 and themounting surface 116 facilitates the subject 132 supplying a compressiveforce to the pedal assembly 122 when the foot of the subject is placedat an angle to a surface normal 115 (see FIG. 1A) of the mountingsurface 116.

In embodiments, the distance between the subject support 118 and themounting surface 116 is adjusted to particular values depending on arelative angle at which the foot of the subject 132 extends relative tothe surface normal 115. For example, in embodiments, the pedal assembly122 may be adjusted such that the foot of the subject 132 may extend atan angle at 0 degrees, 15 degrees, 30 degrees, 45 degrees, and 60degrees relative to the surface normal 115. The surface normal 115 maycoincide with an imaging axis of the imaging system 106 such thataltering the angle of the foot of the subject 132 facilitates imagingdifferent cross-sections of the foot. If the foot is positioned on thepedal assembly 122 such that the foot extends at a 0 degree anglerelative to the surface normal 115, the height adjustment element may beadjusted to possess a minimal length such that the distance between thesubject support 118 and the mounting surface 116 is at a minimum. If thefoot is positioned on the pedal assembly 122 such that the foot extendsat a 15 degree angle relative to the surface normal 115, the heightadjustment element may be adjusted to possess first length that isgreater than the minimal length so that the subject 132 is positionedsome distance above the mounting surface 116. If the foot is positionedon the pedal assembly 122 such that the foot extends at a 30 degreeangle relative to the surface normal 115, the height adjustment elementmay be adjusted to possess second length that is greater than the firstlength, and so on. In embodiments, users of the subject imaging assembly100 may be instructed to adjust the distance between the subject support118 and the mounting surface 116 based on the relative angle of the footbased on a color coding scheme or the like.

The pedal assembly 122 receives a compressive force supplied via a lowerextremity of the subject 132 and provides resistance in response to thecompressive force to simulate a loadbearing condition for the subject132. In embodiments, the pedal assembly 122 comprises an adjustablespring assembly (not depicted) that provides an adjustable amount ofresistance that is specifically tailored to the subject to ensure thatthe subject supplies an adequate amount of compressive force to thepedal assembly 122 to simulate a weightbearing condition for the subject132. For example, in embodiments, the pedal assembly 122 may be adjustedsuch that the subject 132 needs to supply a compressive forcecorresponding to approximately half of the weight of the subject 132 inorder to place the pedal assembly 122 into an imaging state for an imageto be captured. More details regarding the various components of apotential implementation of the pedal assembly 122 are provided hereinwith respect to FIGS. 6A-6F.

As described herein, the substrate 114 and the support platform 102 maytake various forms depending on the implementation. For example, FIG. 2depicts a perspective view of an alternative configuration for thesupport platform 102 and the substrate 114 described herein with respectto FIGS. 1A, 1B, and 1C. As shown, the support platform 102 is supportedby the actuator 128. The actuator 128 is a support arm verticallymovable (e.g., in the z-direction described with respect to FIGS. 1A,1B, and 1C) with respect to the imaging system 106. As depicted, via theactuator 128, the support platform 102 may be positioned such that asupport surface 130 thereof is disposed beneath the opening 110 of thegantry 108. Such a positioning of the support platform 102 mayfacilitate positioning the subject on the support platform 102.

The substrate 114 directly contacts the support surface 130 of thesupport platform 102. For example, the substrate 114 may be mounted tothe support surface 130 via a recess (not depicted) in the supportplatform 102 that is covered by the substrate 114. As described herein,the actuator 128 may include a movable element (not depicted) thatengages with the substrate 114 so as to render the substrate 114 movabletoward the gantry 108. In embodiments, after a subject is positioned onthe substrate 114 (or a subject support disposed thereon), the actuator128 may vertically position the substrate 114 such that the substrate114 is aligned with the opening 110 in the gantry 108 and then move thesubstrate 114 towards the gantry 108 such that a portion of thesubstrate 114 is disposed within the opening 110 for imaging a lowerextremity of a subject.

The substrate 114 may be attached to the support platform 102 via aplurality of different mechanisms. For example, in embodiments, thesubstrate 114 may be coupled to the support platform 102 by any of anumber of different attachment mechanisms at a first end 202 of thesubstrate 114 and at a second end 204 of the substrate 114. As depicted,the first end 202 of the substrate 114 is a proximal end disposed nearthe gantry 108, while the second end 204 is a distal end disposed on thesupport platform 102.

FIG. 3A depicts a side view of a proximal end 302 of a substrate 300. Apedal assembly 306 is disposed on the substrate 300 at the proximal end302. A clip member 304 is attached to an underside surface 308 of thesubstrate 300 via an extension clip 305. In embodiments, the clip member304 is adapted to be inserted into a corresponding attachment element(e.g., a cavity or recess) in a support platform, while the extensionclip 305 may be attached to an actuating element of the supportplatform. For example, FIG. 3B depicts a perspective view of theproximal end 302 of the substrate 300 attached to a support platform 310of an imaging system. As depicted, the substrate 300 may be disposed onan actuating element 314 (e.g., a support table, a scanner bed, etc.) ofthe imaging system. The actuating element 314 may include an opening 316for insertion the extension clip 305. In embodiments, the clip member304 extends over the actuating element 314 and is inserted into anattachment channel 312 of the support platform 310. As such, via theclip member 304, the substrate 300 is secured to the support platform310 in a position proximate to the pedal assembly 306 (not depicted inFIG. 3B).

FIG. 4A depicts an example view of a distal end 402 of a substrate 400of a weightbearing simulation assembly. In embodiments, a subjectsupport (e.g., the subject support 118 described herein with respect toFIGS. 1A, 1B, and 1C) is disposed on the substrate 400 at the distal end402. An underside surface 403 of the substrate 400 includes a recessedmounting member 404 that includes a mounting peg 406. The mounting peg406 is a substantially circular member that may be screwed into anunderside surface 403. The mounting peg 406 includes a mountingprotrusion 408 extending therefrom. In embodiments, the recessedmounting member 404 is adapted to be inserted into a correspondingattachment element of a support platform of a subject imaging assembly.

FIG. 4B depicts an upper surface 411 of a support platform 410 of asubject imaging assembly. An attachment element 412 is disposed on theupper surface 411 and is configured to engage with the recessed mountingmember 404 described herein with respect to FIG. 4A. The attachmentelement 412 includes a protruding portion 414 that is shaped in a mannerthat corresponds to the recessed mounting member 404 disposed on thesubstrate 400. The attachment element 412 also includes a channel 416adapted to receive the mounting peg 406 when the substrate 400 isattached to the support platform 410. The channel 416 includes anopening 418 adapted to receive the mounting protrusion 408 of themounting peg 406 to prevent the substrate 400 from sliding once mountedon the support platform 410. The attachment element 412 includes a pairof slots 420 for fasteners 422 coupling the attachment element 412 tothe support platform 410.

Referring now to FIG. 5A, a perspective view of a weightbearingsimulation assembly 500 is shown. In embodiments, the weightbearingsimulation assembly 500 may be used in conjunction with a subjectimaging assembly (e.g., the weightbearing simulation assembly 500 mayserve as a replacement for the weightbearing simulation assembly 112described herein with respect to FIGS. 1A, 1B, and 1C). Theweightbearing simulation assembly 500 includes a substrate 502 having amounting surface 504. The mounting surface 504 extends a first direction(e.g., the x-direction of the coordinate axes depicted in FIG. 5A). Thefirst direction may correspond to a lengthwise axis of the substrate502. In the depicted embodiment, the mounting surface 504 is a planarflat surface, but the mounting surface 504 may take various formsdepending on the implementation. For example, in embodiments, themounting surface 504 may include a plurality of portions extending indifferent directions or be curved.

The weightbearing simulation assembly 500 also includes a subjectsupport 506 disposed on a first region 508 of the mounting surface 504.The subject support 506 is a seat having a first portion 514 and asecond portion 516 extending at an angle (e.g., about 70 degrees toabout 110 degrees) to the first portion 514. In embodiments, the firstportion 514 and the second portion 516 are integrated into a singlecomponent such that the first portion 514 continuously extends into thesecond portion 516 via a curved transition region 522. In embodiments,the first portion 514 and the second portion 516 are separate componentscoupled to one another via a rotatable connection (not depicted) suchthat the angle between the second portion 516 and the first portion 514may be adjusted to facilitate tilting a subject via the subject support506 (e.g., to move an upper body of the subject away from a gantry of animaging system). The subject support 506 is coupled to the mountingsurface 504 via the first portion 514. In embodiments, the subjectsupport 506 is not directly attached to the mounting surface 504 but toan alternative portion of the substrate 502. For example, the secondportion 516 may be connected to the rear end 524 of the substrate 502via a connection member (not depicted) extending from the second portion516 to the rear end 524. In the depicted embodiment, the first portion514 is coupled to the mounting surface 504 via a translation supportmechanism 526 to facilitate adjusting a distance 515 between the subjectsupport 506 and a pedal assembly 600 in the first direction. Inembodiments, the translation support mechanism may be similar to thetranslation support mechanism 134 described herein with respect to FIGS.1A, 1B, and 1C (e.g., include a pair of tracks, a rotatable supportplatform, a height adjustment element, or the like). As describedherein, the translation support mechanism 526 may enable rotation of thesubject support 506 about at least one axis of rotation. For example,via the translation support mechanism 526, the subject support 506 maybe rotatably coupled to the mounting surface 504 to facilitate rotationof the subject support 506 about a first axis of rotation 520 thatextends substantially perpendicular to the first direction (e.g., in thez-direction of the coordinate axes depicted in FIG. 5A).

Referring now to FIG. 5B, in embodiments, the translation supportmechanism 526 includes a height adjusting element 536 such that thesubject support 506 is separated from the mounting surface 504 by anadjustable distance 532 (e.g., in the z-direction depicted in FIG. 5B)to facilitate adjusting a height of a subject depending on thepositioning of the subject's foot on the pedal assembly 600. Asdepicted, the height adjustment element 536 is disposed on a translatingsupport platform 528 that is coupled to the translation supportmechanism 526. The height adjustment element 536 may include anyadjustable support capable of adjusting the relative positioning betweenthe subject support 506 and the support surface 504. For example, inembodiments, the height adjusting element 536 includes a telescoping armhaving a length that is adjustable in the z-direction so as to renderthe distance 532 adjustable. As described herein, a user may adjust thedistance 532 depending on an orientation of the pedal assembly 600(e.g., a relative angle between the compression direction 626 and thex-direction described herein with respect to FIGS. 6A-6F) to facilitatethe subject supplying a compressive force to the pedal assembly 600while maintaining proper positioning of the subject's foot.

The subject support 506 may include various features to assist a subjectin supplying a load to the pedal assembly 600. For example, the subjectsupport 506 includes handles 517 on the first portion 514 for thesubject to grip while supplying compressive force to the pedal assembly600. In embodiments, the subject support 506 includes a harness assembly550. The harness assembly 550 includes shoulder straps 552 and a lowerrestraint 554. In embodiments, the harness assembly 550 only includesone of either the shoulder straps 552 or the lower restraint 554. Theshoulder straps 552 and/or lower restraint 554 maintain the subject onthe subject support 506 when the subject supplies a compressive force tothe pedal assembly 600. As described herein, the pedal assembly 600 maybe adjusted such that the direction in which the subject suppliescompressive force may be adjusted. When the direction of compressiveforce is at angle to the first direction, application of the compressiveforce by the subject may force the subject upward (e.g., in thez-direction depicted in FIG. 5B). As such, the harness assembly 550 mayprevent the subject from sliding on subject support 506 so that thesubject remains stable for imaging. In embodiments, the handles 517perform such a function in conjunction with the harness assembly 550.Via the handles 517, the subject may stabilize herself while supplyingcompressive force to the pedal assembly 600. The reclining of thesubject support 506 (e.g., via rotation about the second axis ofrotation 518 or adjusting the angle between the first portion 514 andthe second portion 516) facilitates comfortably positioning the subjectirrespective of a positioning of an accompanying imaging system.

The subject provides a compressive force to the pedal assembly 600 via alower extremity (e.g., a foot). In response to the subject providing thecompressive force, the pedal assembly 600 provides an adjustable amountof resistance to ensure that the subject supplies an adequate amount ofcompressive force to simulate a loadbearing condition for the subject.That is, the pedal assembly 600 effectively measures the compressiveforce supplied by the subject to ensure that the subject is supplying anadequate amount of compressive force for imaging. The pedal assembly 600comprises an adjustable spring assembly (not depicted) that provides theadjustable amount of resistance. For example, in embodiments, the pedalassembly 600 may be adjusted to resist movement of the subject's lowerextremity such that the subject is required to exert a compressive forcethat corresponds to approximately half of the weight of the subject inorder to place the pedal assembly 600 into an imaging state. Such aresistance simulates a weightbearing condition for the subject. Thestructure of the pedal assembly 600 is described in more detail withrespect to FIGS. 6A-6F. In embodiments, the weightbearing simulationassembly 500 includes radio-opaque shielding (not depicted) adapted tocover portions of the subject's lower extremity outside of the partbeing image to prevent radiation damage.

FIGS. 6A-6F depict various views of the pedal assembly 600. The pedalassembly 600 includes a spring assembly 602 supported via a pedalsupport assembly 628. The spring assembly 602 includes a contact plate604, compression plate 606, and a first spring member 610 extendingbetween the contact plate 604 and the compression plate 606. The contactplate 604 faces the subject support 506 when the pedal assembly 600 isdisposed on the mounting surface 504 of the substrate 502. A subjectbeing imaged generally places a bottom surface of their foot in contactwith the contact plate 604 to supply a load to the contact plate 604. Asdepicted in FIG. 6B, the contact plate 604 may include a heel cup 694disposed thereon to facilitate the subject positioning the foot properlywith respect to the first spring member 610 to ensure uniformapplication of compressive force to the foot via the spring assembly602. The contact plate 604 may also include an adjustable strap 696 forsecuring the subject's forefoot or midfoot to the contact plate 604 sothat the subject's foot remains stable during imaging while thecompressive force is supplied to the subject's foot. In embodiments, theheel cup 694 and the adjustable strap 696 are rotatably disposed on thecontact plate 604 (e.g., the heel cup 694 and the adjustable strap 696may be part of a foot holding assembly that is rotatably mounted on thecontact plate). In embodiments, the foot holding assembly may be rotatedwith respect to a surface normal 693 of the contact plate 604 to providealternative imaging angles. It should be understood that alternativeembodiments for securing the foot of the subject to the contact plate604 are envisioned. For example, in certain implementations, the contactplate 604 includes an attachment element for an item (e.g., a sock,shoe, etc.) worn by the subject. In an example, the attachment elementmay include Velcro® or the like that is also included on the item wornby the subject.

Referring to FIG. 6B, the contact plate 604 may also include at leastone rotation block 695 disposed thereon. In embodiments, the rotationblock 695 is a triangular wedge adapted to be inserted under a side ofthe subject's foot. In embodiments, the rotation block 695 is rotatableabout an axis (e.g., extending parallel to the surface normal 693) toadjust an orientation of the subject's foot when the foot is alignedalong the rotation block 695. The rotation block 695 may be attached tothe contact plate 604 by any suitable means. For example, inembodiments, the rotation block 695 is attached to the contact plate 604via a removable connection (e.g., Velcro®) to facilitate changing outthe rotation blocks 695. As depicted, in embodiments, the rotation block695 is as attached to the contract plate via an adjustable element 691(e.g., a track, a Velcro® strip, etc.) to render the positioning of therotation block 695 adjustable on the contact plate 604. While thecontact plate 604 is depicted as only incorporating a single rotationblock 695, it should be appreciated that the contact plate 604 mayinclude any number of rotation blocks arranged in a variety of differentconfigurations.

As depicted in FIGS. 6A and 6C, the spring assembly 602 includes thefirst spring member 610 and a second spring member 616. The first andsecond spring members 610 and 616 are attached to the contact plate 604and extend in a compression direction 626 between the contact plate 604and the compression plate 606. The first spring member 610 includes afirst spring 612 and a second spring 614, while the second spring member616 includes a third spring 618 and a fourth spring 620. In embodiments,the first spring 612 and the second spring 614 are cylindrical polymerspring members having axes extending parallel to one another andperpendicular to the compression direction 626. In embodiments, thefirst spring 612 and second spring 614 are selected such that, incombination, the first spring 612 and the second spring 614 provide anamount of force per unit of compression to enable provision ofresistance to simulate a weightbearing condition for the subject. Thesecond spring 614 is coupled to the compression plate 606 via a fastener(not depicted) extending through the second spring 614 and thecompression plate 606. The first spring 612 is coupled to the contactplate 604 via a fastener (not depicted) extending through the firstspring 612 into the contact plate 604. The first spring 612 is attachedto the second spring 614 via a fastener (not depicted) contacting boththe first and second springs 612 and 614. The third and fourth springs618 and 620 of the second spring member 616 may be structured similarlyto the first and second springs 612 and 614 of the first spring member610.

The first and second spring members 610 and 616 are arranged to resistmovement of the contact plate 604 in the compression direction 626responsive to the subject supplying a compressive force to the contactplate 604. The compression direction 626 extends perpendicular to thecontact plate 604 and the compression plate 606. Such an orientation ofthe compression direction 626 with respect to the compression plate 606and contact plate 604 simplifies calibration of the spring assembly 602by applying a force to the subject's foot that corresponds to a flatsurface under gravity, through alternative relative orientations of thecompression direction 626 and the contact plate 604 are possible tosimulate different situations (e.g., an inclined load).

The first and second spring members 610 and 616 are distributed toprovide resistance of motion to an entirety of the subject's foot thatthe subject is required to supply the compressive force to the pedalassembly using substantially the entirety of the subject's foot. Forexample, in embodiments, the first spring member 610 is positioned toresist movement of a first portion of the subject's foot (e.g., themetatarsals) and the second spring member 616 is positioned to resistmovement of a second portion of the subject's foot (e.g., thecalcaneus). This way, the spring assembly 602 ensures that the subjectsupplies approximately 50% of the compressive force using themetatarsals and approximately 50% of the compressive force using theheel. Such a configuration prevents the subject from applying theirweight using only a portion of her foot and ensures that the pedalassembly 600 simulates a true weightbearing condition for the subject.The first and second spring members 610 and 616 may each supply the sameresistance of motion of the contact plate 604 so as to simulate auniform load being supplied across an entirety of the subject's foot. Inembodiments, the first and second spring members 610 and 616 resistmotion of the contact plate 604 in differing amounts to provide acustomized load distribution to the subject's foot.

The number of spring members included in the spring assembly 602 mayvary. For example, certain embodiments may include only a single springmember (e.g., extending between central portions of the contact plate604 and the compression plate 606). Moreover, the first and secondspring members 610 and 616 may possess various alternative structuresthan those depicted. For example, in embodiments, the first and secondspring members 610 and 616 may each only include a single spring. Insuch embodiments, the single spring of the first and second springmembers 610 and 616 may take the form of the first spring 612 describedabove (e.g., a cylindrical polymer spring member having an axis orientedperpendicular to the compression direction 626). Alternatively, thesingle spring may take a different form (e.g., a metal leaf spring, acoil-shaped spring member, an elastic material, etc.). It should beappreciated that the spring assembly 602 may include any number ofsprings in any form consistent with the present disclosure.

In embodiments, the spring assembly 602 may include a sensor (notdepicted) for measuring the compressive force supplied by the subject.For example, in embodiments, the spring assembly 602 comprises apressure sensor adapted to measure the compressive force on the contactplate 604 provided by the subject. The pressure sensor may include apiezoelectric pressure sensor, an electromagnetic pressure sensor, anoptical pressure sensor, a capacitive pressure sensor, or any otheravailable pressure sensor adaptable to measure the compressive forcesupplied via the foot of the subject. In embodiments, the springassembly 602 may include a plurality of pressure sensors to measure thepressure supplied via the subject at various portions of the contactplate 604 (e.g., corresponding to the portions of the contact plate 604overlapping the first and second spring members 610 and 616).Alternatively or additionally, the spring assembly 602 may include aforce sensor configured to measure a total force applied to the contactplate 604. In certain embodiments where the spring assembly 602incorporates such a sensor, the spring assembly 602 may not include thefirst and second spring members 610 and 616 and the pedal assembly 600may provide an indication via the sensor (e.g., via a light or soundgenerator coupled to the sensor) of when the subject has supplied adesired amount and distribution of compressive force to the contactplate 604 for imaging.

The spring assembly 602 also includes a first motion limiter 622 and asecond motion limiter 624 coupled to the compression plate 606 via anadjustable assembly 650. As depicted in FIG. 6E, when the springassembly 602 is in an unloaded state (e.g., when the subject does notsupply a compressive to the contact plate 604) the contact plate 604 andthe compression plate 606 are separated by a first distance 153 in thecompression direction 626 and the first and second spring members 610and 616 contact both the contact plate 604 and the compression plate606. In embodiments, the first and second spring members 610 and 616 maynot contact the contact plate 604 when the spring assembly 602 is in theunloaded state (e.g., the first and second spring members 610 and 616may only be connected to the compression plate 206 in such embodiments).When the spring assembly 602 is in the unloaded state, ends 623 and 635of the first and second motion limiters 622 and 624 are disposed betweenthe contact plate 604 and the compression plate 606. The positioning ofthe ends 623 and 625 of the first and second motion limiters 622 and 624determines a range of motion of the contact plate 604 relative to thecompression plate 606.

As depicted in FIG. 6D, when the spring assembly 602 is in a loadedstate (e.g., when a subject supplies compressive force to sufficientlycompress the first and second spring members 610 and 616) the contactplate 604 contacts the ends 623 and 625 of the first and second motionlimiters 622 and 624. The first and second motion limiters 622 and 624may be secured within the pedal support assembly 628 such that first andsecond motion limiters 622 and 624 are stationary relative to thecompression plate 606 and the positioning of the ends 623 and 625 of themotion limiters 622 and 624 determines a range of motion of the contactplate 604. When the spring assembly 602 is in the loaded state, thecontact plate 604 and the compression plate 606 are separated by asecond distance 151 in the compression direction 626 and the first andsecond spring members 610 and 616 resist movement of contact plate 604in an amount that is proportional to the amount of displacement of thecontact plate 604 caused by the subject. In other words, the differencebetween the first distance 153 between the contact plate 604 and thecompression plate 606 when the spring assembly 602 is in an unloadedstate and the second distance 151 between the contact plate 604 and thecompression plate 606 when the spring assembly is in a loaded statedetermines the resistance to the subject's foot applied via the springassembly 602.

In embodiments, the positioning of the first motion limiter 622 and thesecond motion limiter 624 relative to the compression plate 606 (andtherefore the amount of compressive force supplied via the springassembly 602 when the spring assembly 602 is placed in the loaded state)is adjustable via the adjustable assembly 650. As shown in FIGS. 6A and6C, the adjustable assembly 650 is a gear assembly comprising a firstdriving gear 654 and a second driving gear 658 that are attached to afixed plate 652 via the first and second motion limiters 622 and 624. Inembodiments the first and second motion limiters 622 and 624 includethreaded rods extending through the contact plate 604, the first andsecond driving gears 654 and 658, respectively, and the fixed plate 652.The first and second motion limiters 622 and 624 may extend throughthreaded openings 605 and 607 in the contact plate 604 such thatrotation of the driving gears 654 and 658 adjusts the positioning of thefirst and second motion limiters 622 and 624 in the compressiondirection 626. The first driving gear 654 is in engagement with a firstlower gear 656 that is coupled to the fixed plate 652 via a shaft 672.The second driving gear 658 in engagement with a second lower gear 660that is coupled to the fixed plate 652 via a shaft 674. The first lowergear 656 is attached to a first upper gear 664 that also attached to thefixed plate 652 via the shaft 672. The second lower gear 660 is attachedto a second upper gear 666 that is also attached to the fixed plate viathe shaft 674. The first and second upper gears 664 and 666 are both inengagement with a central gear 662 that is attached to an adjustmentknob 670 via a shaft 668 extending through the fixed plate 652. As such,rotation of the adjustment knob 670 by a user causes rotation of thecentral gear 662, which in turn causes rotation of the upper and lowergears 656, 660, 664, and 666, and rotation of the first and second lowergears 656 and 660 in turn causes rotation of the first and seconddriving gears 654 and 658 to rotate the first and second motion limiters622 and 624 and adjust the positioning of the first and second motionlimiters 622 and 624 in unison to adjust the compressive force suppliedvia the spring assembly 602 when the spring assembly is placed in theloaded state depicted in FIG. 6D. The adjustable assembly 650 ensuresalignment between the first and second motion limiters 622 and 624 suchthat a uniform compressive force is supplied to the contact plate 604via the spring assembly 602. Moreover, the multi-gear coupling of theadjustable assembly 650 facilitates fine tuning of the positioning ofthe first and second motion limiters 622 and 624 so that the compressiveforce may be accurately tuned. Alternative embodiments of the adjustableassembly 650 are envisioned. For example, in embodiments, the adjustableassembly 650 may include a different gear assembly having more or fewerelements than the adjustable assembly depicted in FIGS. 6A-6C. Anexample of an alternative gear assembly is described herein with respectto FIG. 8. In embodiments, the first and second motion limiters 622 and624 are independently adjustable. For example, each of the first andsecond motion limiters 622 and 624 may each be attached an independentlyadjustable gear assembly having an independent adjustment knob. Inembodiments, the adjustable assembly 650 may include an actuatorconfigured to electrically adjust the adjustment knob 670 (or any otherelement that can be manipulated) in response to a user input. Inembodiments, the adjustable assembly 650 or spring assembly 602 mayinclude a sensor, detector, or the like, and may provide an output basedon a compressive force supplied by the subject (e.g., measuring anamount of compressive force). In embodiments, the adjustable assembly650 may include a translating assembly coupled to the contact plate 604.

The pedal support assembly 628 includes a first side plate 630 and asecond side plate 632 that define a channel 634 in which the springassembly 602 is disposed. The first side plate 630 includes slots 638and 644 for receiving fasteners (not depicted) that extend into a firstside edge 636 of the contact plate 604. The second slide plate 632includes slots 642 and 646 for receiving fasteners (not depicted) thatextend into a second side edge 640 of the contact plate 604. The slots638, 642, 644, and 646 extend in the compression direction 626 tofacilitate movement of the contact plate 604 relative to the compressionplate 606. In embodiments, the compression plate 606 and the fixed plate652 are also attached to the first and second side plates 630 and 632via fasteners (not depicted) extending through the first and second sideplates 630 such that the fixed plate 652 and the compression plate 606are fixed in relation to the contact plate 604. It should be appreciatedthat a number of alternative structures for the pedal support assembly628 are envisioned. For example, in embodiments, the pedal supportassembly 628 includes a support carriage (not depicted) that directlycontacts the substrate 502 along a contact distance for directlyattaching the pedal support assembly 628 to the substrate 502. Thesupport carriage may include side walls having structures similar to thefirst and second side plates 630 and 632 to facilitate supporting thespring assembly 602.

As depicted in FIG. 6A, the pedal support assembly 628 is oriented suchthat the contact plate 604 and the compression plate 606 extend largelyin the y-z plane defined by the coordinate axes of FIG. 6A. In such anorientation, the contact plate 604 and the compression plate 606 extendsubstantially perpendicular to the mounting surface 504 of the substrate502 depicted in FIG. 5A. Such an orientation may be useful for imagingthe subject's ankle. However, it may be also be useful to image thesubject's foot in alternative orientations. For example, it may beuseful to adjust the orientation of the spring assembly 602 such thatthe contact plate 604 and the compression plate 606 extend at an anglerelative to the z-direction of the coordinate axes of FIG. 6A of about30 degrees or about 60 degrees or any angle between and including zerodegrees and 60 degrees to facilitate imaging various portions (e.g., theangle, forefoot, and hindfoot) of the subject's foot. In this regard,the pedal support assembly 628 is supported by an adjustable supportelement 698 (see FIG. 6C) having a plurality of support positions 682.In embodiments, the user may select from among the plurality of supportpositions 682 to change the orientation of the spring assembly 602(e.g., to adjust a relative angle between the compression direction 626and a direction of extension of the substrate 502).

As depicted in FIG. 6C, the adjustable support element 698 includes afirst propping plate 678 and a second propping plate 680 coupled to oneanother via the spring assembly 602 and a rear brace 686 extendingbetween the first and second propping plates 678 and 680. Inembodiments, the first and second propping plates 678 and 680 aredirectly attached to the mounting surface 504 of the substrate 502. Asdepicted in FIG. 6B, the adjustable support element 698 includesopenings 699 at a pivot axis 692 of the pedal support assembly 628. Inembodiments, a connection rod (not depicted) extends through theopenings 699 at the pivot axis 692 and through corresponding openings697 in a first portion 688 of the pedal support assembly 628 (see FIG.6E) to rotatably couple the first portion 688 to the adjustable supportelement 698. A second portion 690 of the pedal support assembly 628 iscoupled to the adjustable support element 698 at one of the supportpositions 682 via a propping rod 684. In embodiments, a user may removethe propping rod 684 from a first one of the support positions 682,realign the pedal support assembly 628 with respect to the adjustablesupport element 698 such that the second portion 690 is aligned withrespect to a second one of the support positions 682, and re-insert thepropping rod 684 through the second portion 690 to adjust theorientation of the spring assembly 602. In embodiments, the plurality ofsupport positions 682 extend in equally spaced angular intervals alongan arc. In the example depicted, by selecting from among the pluralityof support positions 682, a user may adjust the orientation of thecompression direction 626 in angular (e.g., about 30 degree) incrementswith respect to the z-direction of the coordinate axes of FIG. 6B (e.g.,about 0 degrees, about 30 degrees, about 60 degrees, or the like).

FIG. 6F depicts a perspective view of the pedal assembly 600 where thepropping rod 684 is inserted into a support position of the plurality ofsupport positions 682 of the adjustable support element 698 that is mostproximate to the mounting surface 504 of the weightbearing simulationassembly 500. As depicted, in such a configuration, the compressiondirection 626 is angled approximately 45 degrees relative to the firstdirection (e.g., the x-direction depicted in FIG. 6F) to facilitateimaging a hindfoot of the subject. In embodiments, when the pedalassembly 600 is oriented in the manner depicted in FIG. 6F, otheradjustments to the weightbearing simulation assembly 500 are made tofacilitate imaging. For example, referring to FIG. 5B, the heightadjusting element 536 may be adjusted such that the adjustable distance532 is greater when the pedal assembly 600 is oriented as depicted inFIG. 6F than when the pedal assembly 600 is oriented as depicted inFIGS. 6A-6B. In embodiments, when one of the plurality of supportpositions 682 of the adjustable support element 698 is selected (e.g.,to select a particular orientation of the compression direction 626),the adjustable distance 532 is adjusted to a particular value based onthe selected orientation of the compression direction 626 in accordancewith a predetermined orientation-height scheme.

Alternatives to adjustable support element 698 are envisioned. Forexample, in embodiments, the pedal support assembly 628 is disposeddirectly on the substrate 502 and not supported by the adjustablesupport element 698, which may result in an orientation of the pedalassembly 600 where the compression direction 626 extends at a non-zeroangle (e.g., about 60 degrees) from the z-direction of the coordinateaxes of FIGS. 6A and 6B. In such embodiments, the entirety of the pedalsupport assembly 628 may be disposed on a rotatable platform tofacilitate angular adjustment of the spring assembly 602. Alternatively,an alternative adjustable support element may be used. An example ofsuch an alternative support element is described herein with respect toFIG. 9.

Referring now to FIG. 7, a perspective view of a motion limiter 700 isdepicted. In embodiments, the motion limiter 700 may be used in place ofat least one of the first and second motion limiters 622 and 624depicted in FIGS. 6A-6F. The motion limiter 700 includes a threaded rod702 having a plunger 704 disposed in an opening 708 formed within thethreaded rod 702. A spring element 706 supports the plunger 704 withinthe opening 708. In embodiments, the spring element 706 is attached to acompression plate (e.g., the compression plate 606) of a spring assembly(e.g., the spring assembly 602). For example, in embodiments, the springassembly 602 includes two of the motion limiters 700 in place of thefirst and second motion limiters 622 and 624. The plunger 704 of eachmotion limiter 700 extends from the compression plate 606 and issupported by the spring element 706 such that the end 710 of the plunger704 extends outward from the threaded rod 702. In operation, once thesubject supplies the load to the contact plate 604 and the contact plate604 contacts the motion limiter 700, the contact plate 604 initiallycompresses the spring element 706 via contacting the end 710 of theplunger 704. The spring element 706 beneficially dampens the impactbetween the contact plate 604 and the motion limiter 700.

Referring now to FIG. 8, a perspective view of a gear assembly 800 for apedal assembly of a weightbearing simulation assembly is depicted. Forexample, in embodiments, the gear assembly 800 may be used in place ofthe adjustable assembly 650 described herein with respect to FIGS.6A-6F. The gear assembly 800 includes a first driving gear 808 and asecond driving gear 810. The first and second driving gears 808 and 810may be coupled motion limiters of the spring assembly (not depicted)extending through a compression plate 804. The first and second drivinggears 808 and 810 are each mechanically engaged to a central gear 806such that rotation of the central gear 806 causes a rotation of themotion limiters coupled to the first and second driving gears 808 and810 and an adjustment in the positioning of the motion limiters. A gearcover 812 (e.g., in place of the fixed plate 652 described with respectto FIGS. 6A-6F) covers the adjustable gear assembly 800 to protect thegear assembly 800 from dust or other debris to ensure long-termoperation. The gear assembly 800 has fewer components than theadjustable assembly 650 described with respect to FIGS. 6A-6F, but doesnot enable as fine of adjustment of the compressive force supplied byspring assembly.

Referring now to FIG. 9, another pedal assembly 900 is depicted. Thepedal assembly 900 may be used in place of the pedal assembly 600described herein with respect to FIGS. 6A-6F. The pedal assemblyincludes a spring assembly 902 having a contact plate 904 and acompression plate 906 separated by a first motion limiter 908 and asecond motion limiter (not depicted). In embodiments, the first motionlimiter 908 is coupled to the compression plate 906 via the gearassembly 800 (e.g., the first driving gear 808) described with respectto FIG. 8. The spring assembly 902 includes a spring member (notdepicted) extending in a compression direction 916 between the contactplate 904 and the compression plate 906.

The pedal assembly 900 includes a pedal support assembly 910 thatincludes a first side plate 912 and a second side plate 914. The firstand second side plates 912 and 914 are shaped to be disposed directly onthe mounting surface 504 of the substrate 502 of the weightbearingsimulation assembly 500. As depicted, the first and second side plates912 and 914 are oriented such that, when disposed on the mountingsurface 504, the compression direction 916 extends at an angle to themounting surface 504. To adjust the relative angle between thecompression direction 916 and the mounting surface 504, the pedalsupport assembly 910 includes an adjustable support element 918. Theadjustable support element 918 includes a first pair of elevation blocks920 and a second pair of elevation blocks 922. The first pair ofelevation blocks 920 have a smaller dimension (e.g., length) than thesecond pair of elevation blocks 922. In embodiments, both the first andsecond pairs of elevation blocks 920 and 922 are rotatable with respectto the pedal support assembly 910. In the depicted configuration, thefirst and second pairs of elevation blocks 920 and 922 are disposed onthe mounting surface 504 and do not support the pedal support assembly910. In embodiments, a user may rotate either first pair of elevationblocks 920 or the second pair of elevation blocks 922 such that eitherthe first pair of elevation blocks 920 or the second pair of elevationblocks 922 supports a rear brace 924 of the pedal support assembly 910to adjust the relative angle between the compression direction 916 andthe mounting surface 504.

Referring now to FIG. 10 a flow diagram of an illustrative method 1000for capturing a load-bearing image of a lower extremity of a subject isshown. The method 1000 may be performed via the weightbearing simulationassembly 500 described herein used in combination with a subject imagingassembly. For example, in embodiments, the weightbearing simulationassembly 500 may disposed on the support platform 102 of the subjectimaging assembly 100 described herein with respect to FIGS. 1A-1C tocapture a load-bearing image of the lower extremity of the subject viaperformance of the method 1000. In embodiments, the weightbearingsimulation assembly 500 may be calibrated prior to performance of themethod 1000. For example, practice weights may be applied to the pedalassembly 600 to calibrate the settings for the spring assembly 602(e.g., to determine positioning for the first and second motion limiters622 and 624 necessary to resist the compressive force supplied byvarious subjects and simulate a weightbearing condition).

At block 1002, a subject is positioned on the subject support 506 of aweightbearing simulation assembly 500. In embodiments, the weightbearingsimulation assembly 500 may be disposed on the support platform 102,which may be positioned (e.g., via the actuator 128 as described withrespect to FIG. 2) out of alignment with the imaging system 106 tofacilitate positioning the subject on the subject support 506.Additionally, the subject support 506 may be rotatable about a firstaxis of rotation 520 to make it easier to position the subject on theweightbearing simulation assembly 500.

At block 1004, the weightbearing simulation assembly 500 is adjustedbased on the subject and imaging requirements. For example, inembodiments, the distance 515 between the subject support 506 and thepedal assembly 600 is adjusted based on a length of the subject's leg tobe imaged. In embodiments, the distance 515 is adjusted such that thesubject's leg extends in the first direction (e.g., the x-directiondepicted in FIG. 5A) and substantially the entirety of the subject's legis in contact with the mounting surface 504 of the substrate 502. Inembodiments, the subject support 506 may be tilted about the second axisof rotation 518 based on an imaging angle of the gantry 108. Inembodiments, a relative angle between the first direction and thecompression direction 626 of the pedal assembly 600 may be adjusted(e.g., by selecting a support position 682 of the adjustable supportelement 698) based on a portion of the subject's lower extremity beingimaged. For example, in embodiments, to image an ankle of the subject, afirst support position 682 is selected to place the compressiondirection 626 at a zero degree angle (e.g., parallel or substantiallyparallel) to the first direction. In embodiments, to image a forefoot ofthe subject, a second support position 682 is selected to place thecompression direction 626 at a 30 degree angle relative to the firstdirection. In embodiments, to image a hindfoot of the subject, a thirdsupport position 682 is selected to place the compression direction 626at a 45 degree angle relative to the first direction.

In embodiments adjustment of the weightbearing simulation assembly 500also includes adjusting positions of the first and second motionlimiters 622 and 624 between the contact plate 604 and the compressionplate 606 based on a weight of the subject. As described herein,adjustment of the first and second motion limiters 622 and 624determines a compressive force supplied via the first and second springmembers 610 and 616 to the contact plate 604 when the subject supplies aload to the contact plate 604. The load supplied by the subject causesthe contact plate 604 to contact ends 623 and 625 of the first andsecond motion limiters 622 and 624. As such, the positioning of the ends623 and 625 determines the compressive force supplied via the first andsecond spring members 610 and 616. In embodiments, the spring assembly602 is calibrated via placing a scale in contact with the contact plate604 and using the scale to measure the compressive force supplied viathe first and second spring members 610 and 616 as a function of therotational position of the adjustment knob 670. In embodiments,adjustment of the weightbearing simulation assembly 500 includesrotating the adjustment knob 670 to a position such that the compressiveforce supplied via the first and second spring members 610 and 616corresponds to approximately one half of the weight of the subject.

In a block 1006, the subject is secured to the weightbearing simulationassembly 500. For example, in embodiments, the subject's foot is securedto the pedal assembly 600 via placement of the subjects heel on the heelcup 694 and tightening the adjustable strap 696 around the subject'sfoot. Additionally, the subject may be secured to the subject support506 via a shoulder strap or the like to assist the subject in supplyingthe load to the pedal assembly 600. At block 1008, the weightbearingsimulation assembly 500 is positioned for imaging. For example, inembodiments, the actuator 128 of the support platform 102 is used tomove the weightbearing simulation assembly 500 in the first directiontowards the imaging system 106 such that the pedal assembly 600 isdisposed within the opening 110 of the gantry 108 and the subject'slower extremity to be imaged is within a field of view of the imagingsystem 106.

In a block 1010, the subject is instructed to apply a force to the pedalassembly 600. For example, once the pedal assembly 600 is placed withinthe imaging system 106, the subject may be instructed to press her footinto the contact plate 604 so as to compress the first and second springmembers 610 and 616 in the compression direction 626. The instructionsmay be automated (e.g., transmitted via a speaker system). In a block1012, once the subject causes the contact plate 604 to contact the firstand second motion limiters 622 and 624, thereby causing the first andsecond spring members 610 and 616 to exert a compressive forcespecifically tailored to the subject, an image is captured of thesubject's lower extremity. The imaging system 106 may capture a CT scanor an MRI image of the subject's lower extremity while the lowerextremity is in a weightbearing condition so as to capturethree-dimensional structural measurements of the subject's lowerextremity.

In view of the foregoing description, it should be appreciated thatweightbearing simulation assemblies that are compatible with existingimaging systems may be used to capture three dimensional images of lowerextremities of subjects while the lower extremities are in a loadbearingcondition. The weightbearing simulation assemblies described hereininclude a pedal assembly with an adjustable spring assembly. The springassembly disclosed herein is easily adjustable by altering the relativepositioning of motion limiters disposed between a contact plate and acompression plates so as to limit the range of motion of the contactplate such that, when the spring assembly is placed in a loaded state bythe subject, the spring assembly applies a compressive force to thecontact plate that is specifically tailored to the subject. Moreover, arelative angle between the compressive force and an imaging axis of theimaging system may be adjusted to facilitate imaging multiple regions ofthe subject's foot. As such, the assemblies and methods described hereinfacilitate low cost load-bearing images at relatively low cost byproviding compatibility with existing imaging systems.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the embodiments describedherein without departing from the spirit and scope of the claimedsubject matter. Thus, it is intended that the specification cover themodifications and variations of the various embodiments described hereinprovided such modification and variations come within the scope of theappended claims and their equivalents.

What is claimed is:
 1. A weightbearing simulation assembly comprising: asubstrate comprising a mounting surface extending in a first direction;a subject support disposed on a first region of the mounting surface;and a pedal assembly disposed on a second region of the mountingsurface, wherein the pedal assembly is spaced apart from the subjectsupport by a distance in the first direction, the pedal assemblycomprising: a spring assembly comprising a contact plate facing thesubject support, a compression plate, and a first spring disposedbetween the contact plate and the compression plate, the springextending in a compression direction; a first motion limiter extendingthrough the compression plate, wherein an end of the first motionlimiter is disposed between the compression plate and the contact plateto limit a range of motion of the contact plate in the compressiondirection, wherein the contact plate contacts the first motion limiterat an end of the range of motion to place the first spring into a loadedstate when a subject applies a compressive force to the contact plate; apedal support assembly disposed on the mounting surface, the pedalsupport assembly defining a cavity in which the spring assembly isdisposed; and an adjustable support element for the pedal supportassembly, the adjustable support element comprising a plurality ofsupport positions selectable to adjust an orientation of the pedalsupport assembly to change a relative angle between the compressiondirection and the first direction.
 2. The weightbearing simulationassembly of claim 1, wherein the first spring resists motion of a firstportion of the contact plate configured to support a forefoot of asubject, wherein the spring assembly further comprises a second springthat resists motion of a second portion of the contact plate configuredto support a heal of the subject such that the spring assembly isconfigured to resist motion of the contact plate along an entire lengthof a foot of the subject.
 3. The weightbearing simulation assembly ofclaim 2, wherein the first and second springs each comprise a pair ofpolymer spring members, wherein each pair of spring members comprises: afirst polymer spring member attached to the compression plate, the firstpolymer spring member having an axis aligned perpendicular to thecompression direction; and a second polymer spring member attached tothe first spring member and extending between the first spring memberand the contact plate, the second polymer spring member having an axisaligned substantially parallel to the axis of the first polymer springmember.
 4. The weightbearing simulation assembly of claim 1, wherein thepedal support assembly comprises a first side plate and a second sideplate defining the cavity, wherein a first end of the contact pate iscoupled to the first side plate via a first mounting slot of the firstside plate extending in the compression direction, wherein a second endof the contact plate is coupled to the second side plate via a firstmounting slot of the second side plate extending in the compressiondirection.
 5. The weightbearing simulation assembly of claim 4, whereinfirst and second side plates further comprise second mounting slotsextending in the compression direction that are offset from the firstmounting slots of the first and second side plates, respectively,wherein the first end of the contact pate is coupled to the first sideplate via the second mounting slot of the first side plate, wherein thesecond end of the contact plate is coupled to the second side plate viathe second mounting slot of the second side plate.
 6. The weightbearingsimulation assembly of claim 1, wherein the first motion limiter iscoupled to the pedal support assembly via an adjustable assembly havingan having an attachment element aligned with a first opening in thecompression plate, wherein the first motion limiter extends through thefirst opening in the compression plate and is manipulable via theadjustable assembly so as to adjust a distance between the end of thefirst motion limiter and the compression plate to change the range ofmotion of the contact plate.
 7. The weightbearing simulation assembly ofclaim 6, wherein the adjustable assembly comprises a gear assemblycoupled to the pedal support assembly via a fixed plate, wherein thefirst motion limiter comprises a first threaded rod extending throughthe first opening in the compression plate, wherein the first threadedrod is attached to a first driving gear that is rotatable via adjustmentof a knob coupled to the first driving gear via the gear assembly,wherein the first opening in the compression plate is threaded such thatrotation of the first driving gear via adjustment of the knob changes aposition of the end of the first motion limiter in the compressiondirection.
 8. The weightbearing simulation assembly of claim 7, furthercomprising a second motion limiter comprising a second threaded rodextending through a second threaded opening in the compression plate,wherein the second motion limiter is attached to a second driving gearthat is rotatable via adjustment of the knob coupled to the seconddriving gear via the gear assembly, wherein the rotation of the seconddriving gear via adjustment of the knob changes a position of an end ofthe second motion linear in conjunction with the end of the first motionlimiter such that the ends of the first and second motion limiters areequidistant from the compression plate in the compression direction. 9.The weightbearing simulation assembly of claim 1, wherein the pedalsupport assembly comprises a first portion in contact with the mountingsurface irrespective of the support position of the adjustable supportelement and a second portion, wherein the pedal support assembly pivotsabout a pivot axis extending through the first portion to facilitateselection among the plurality of support positions of the adjustablesupport element.
 10. The weightbearing simulation assembly of claim 9,wherein the adjustable support element comprises a pair of proppingplates coupled to the second portion of the pedal support assembly via apropping pin, wherein the plurality of support positions of theadjustable support element comprise a plurality of pairs of holesextending through the propping plates.
 11. The weightbearing simulationassembly of claim 1, wherein the subject support comprises a seat havinga first portion coupled to the mounting surface and a second portionextending at an angle to the first portion, wherein the first portion iscoupled to the mounting surface via translation support mechanism so asto render the distance in the first direction between the subjectsupport and the pedal assembly adjustable.
 12. The weightbearingsimulation assembly of claim 11, wherein the first portion of thesubject support is mounted to the translation support mechanism suchthat the first portion is rotatable about an axis of rotation.
 13. Asubject imaging assembly comprising: a support platform extending in afirst direction, the support platform comprising an engagement element;an imaging system comprising a gantry, the gantry comprising an opening;a weightbearing simulation assembly disposed on the support platform,the weightbearing simulation assembly comprising: a substrate coupled tothe engagement element of the support platform, the substrate comprisinga mounting surface extending in the first direction; a subject supportdisposed on a first region of the mounting surface, the subject supportrotatable about an axis of rotation to facilitate positioning thesubject support relative to the gantry; and a pedal assembly disposed ona second region of the mounting surface, wherein the pedal assembly isspaced apart from the subject support by a distance in the firstdirection, the pedal assembly comprising: a spring assembly comprising acontact plate facing the subject support, a compression plate, and aspring disposed between the contact plate and the compression plate, thespring extending in a compression direction; a motion limiter extendingfrom the compression plate, wherein an end of the motion limiter isdisposed between the compression plate and the carrier plate to limit arange of motion of the contact plate in the compression direction; apedal support assembly disposed on the mounting surface, the pedalsupport assembly supporting the spring assembly on the mounting surface;and an actuator coupled to the substrate of the weightbearing simulationassembly, the actuator configured to move the weightbearing simulationassembly in the first direction such that the pedal assembly is disposedwithin the opening to generate an image.
 14. The subject imagingassembly of claim 13, wherein the subject support comprises a seathaving a first portion coupled to the mounting surface and a secondportion extending at an angle to the first portion, wherein the firstportion is coupled to the mounting surface via translation supportmechanism so as to render the distance in the first direction betweenthe subject support and the pedal assembly adjustable.
 15. The subjectimaging assembly of claim 14, wherein the first portion of the subjectsupport is mounted to the translation support mechanism such that thefirst portion is rotatable about an axis of rotation in a seconddirection substantially perpendicular to the first direction so as totilt the subject away from the pedal assembly.
 16. The subject imagingassembly of claim 13, wherein the pedal assembly further comprises anadjustable support element for the pedal support assembly, theadjustable support element comprising a plurality of support positionsselectable to adjust an orientation of the pedal support assembly tochange a relative angle between the compression direction and the firstdirection.
 17. A method of capturing an image of a lower extremity of asubject, the method comprising: positioning a subject on a subjectsupport of a weight simulation assembly disposed on a support platformof an imaging system, wherein the weight simulation assembly comprises asubstrate extending in the first direction, a subject support disposedon a first region of the substrate, and a pedal assembly disposed on asecond region of the substrate, wherein the pedal assembly is spacedapart from the subject support by a distance in the first direction;adjusting a motion limiter disposed between a contact plate facing thesubject support and a compression plate of the pedal assembly so as tochange a range of motion of the contact plate within the pedal assemblyin a compression direction and create a load tailored to the subjectwhen the contact plate is in a fully pressed position; adjusting arelative angle between the compression direction and the first directionso as to adjust an angle of the lower extremity in the pedal assembly;positioning the weightbearing simulation assembly relative to a gantryof an imaging system such that the pedal assembly is disposed within anopening of the gantry; and once the subject applies the load tailored tothe subject to the contact plate via the lower extremity so as to bringthe contact plate in contact with the motion limiter, capturing an imageof the lower extremity using the imaging system.
 18. The method of claim17, wherein adjusting the motion limiter comprises rotating a knobcoupled to a gear assembly to rotate a driving gear coupled to themotion limiter.
 19. The method of claim 17, wherein adjusting therelative angle between the compression direction and the first directioncomprises selecting a support position of an adjustable support elementcoupled to a pedal support assembly holding the contact plate and thecompression plate and rotating a pivoting portion of the pedal supportassembly disposed on the substrate to align a second portion of thepedal support assembly with the selected support position.
 20. Themethod of claim 17, further comprising adjusting an orientation of thelower extremity on the contact plate by adjusting a rotation blockdisposed on the contact plate.